1. Field of the Invention
The present invention relates to a microchip useful as μ-TAS (Micro Total Analysis System) preferably used for a biochemical test of DNA, protein, a cell, immunity and blood, chemical synthesis and environmental analysis.
2. Description of the Background Art
In recent years, importance of sensing, detecting or determining vital substances such as DNA Deoxyribo Nucleic Acid), an enzyme, an antigen, an antibody, protein, a virus and a cell and a chemical substance has increased in the fields of medical care, health, food and chemical production, and various biochips and microchemical chips (hereinafter these are generically referred to as microchips) capable of simply measuring the same are proposed. A microchip, capable of conducting a series of experimental/analytical operations conducted in a laboratory within a chip of several cm to 10 cm square having a thickness of about several mm to several cm, has such various advantages that the quantities of a specimen and a reagent may be small, the cost is low, the reaction rate is high, a test can be conducted at a high throughput, and a test result can be immediately obtained on the site where the specimen has been collected.
The microchip has a fluid circuit therein, and this fluid circuit can be mainly constituted of portions such as a liquid reagent holding portion holding a liquid reagent for mixing or reacting with a specimen (blood can be listed as an example thereof) or for treating the specimen, a measuring portion measuring the specimen and the liquid reagent, a mixing portion mixing the specimen and the liquid reagent with each other and a detecting portion for conducting analysis and/or a test as to the mixed liquid and a fine flow channel (having a width of about several 100 μm, for example) properly connecting these portions with each other. The microchip is typically placed on an apparatus (centrifugal apparatus) capable of applying centrifugal force thereto and used. Fluid treatments such as measurement of the specimen and the liquid reagent, mixture, and introduction of the mixed liquid into the detecting portion can be performed by applying centrifugal force of a proper direction to the microchip (refer to Japanese Patent Laying-Open No. 2007-017342, for example).
Test/analysis (detection of a specific component in the mixed liquid, for example) of the mixed liquid introduced into the detecting portion can be performed by optical measurement of applying detecting light to the detecting portion in which the mixed liquid is stored and measuring the transmittance thereof, for example (refer to Japanese Patent Laying-Open No. 2006-300741, for example).
In a microchip for a blood test, for example, various tests are generally conducted with a blood plasma component in blood, and hence the fluid circuit of the microchip generally includes a blood plasma separation portion (centrifugation portion) for removing a blood cell component from the blood introduced into the fluid circuit by centrifugation and separating and extracting a blood plasma component. In order to separate a blood plasma and a blood cell from the blood, there are a blood cell separation filter and a method of performing extraction after centrifugation, for example.
A microchip comprising a centrifugal tube for extracting a target component from a sample introduced into a fluid circuit is disclosed in the pamphlet of International Patent Laying-Open No. 05/033666. FIGS. 29, 30, 31, 32, 33 and 34 are schematic step diagrams showing an operating method of the microchip disclosed in the pamphlet of International Patent Laying-Open No. 05/033666. The fluid circuit of the microchip shown in FIGS. 29, 30, 31, 32, 33 and 34 is mainly constituted of an intake 1 for introducing the sample into the fluid circuit, a centrifugal tube 2 connected to intake 1, an adjusting tube 3 consisting of an adjusting tube connecting portion 3a and a reservoir portion 3b, a first weighing portion 4 for measuring the extracted target component, reagent reservoirs 6a and 6b in which a reagent 5 is stored, a primary mixing portion 7 and a secondary mixing portion 8 in which mixing of the target component and reagent 5 is performed and a photodetection channel 9 for conducting test/analysis as to the obtained mixed liquid, and centrifugal tube 2 has a first holding portion 10 for mainly storing a component (nontarget component) other than the target component (see FIG. 29). An outline of the operating method of this microchip is now described with reference to FIGS. 29, 30, 31, 32, 33 and 34.
First, a sample 11 is introduced from intake 1, so that centrifugal tube 2 and adjusting tube connecting portion 3a are filled up (see FIG. 29). Then, the microchip is so rotated around a first rotating axis 12 as to centrifuge sample 11 closer to centrifugal tube 2 than a boundary B-B′ in centrifugal tube 2 (see FIG. 30). At this time, a nontarget component 14 other than a target component 13 in sample 11 is stored in first holding portion 10. Sample 11 closer to adjusting tube 3 than boundary B-B′ is introduced into reservoir portion 3b. Reagent 5 having been stored in reagent reservoirs 6a and 6b is introduced into primary mixing portion 7 due to this rotation around first rotating axis 12.
Then, the microchip is so rotated around a second rotating axis 15 as to introduce centrifuged target component 13 into first weighing portion 4 from centrifugal tube 2 (see FIG. 31). Target component 13 overflowing first weighing portion 4 is introduced into a waste liquid reservoir 16 connected to first weighing portion 4. Then, the microchip is rotated around first rotating axis 12 again, thereby introducing target component 13 in first weighing portion 4 into primary mixing portion 7 and mixing the same with reagent 5 (see FIG. 32).
Then, a mixed substance 17 as obtained is introduced into secondary mixing portion 8 by sucking the same from a suction port 9a with a pump and further mixed (see FIG. 33), and mixed substance 17 is introduced into photodetection channel 9 (see FIG. 34). Mixed substance 17 introduced into photodetection channel 9 is subjected to optical measurement such as that of introducing light from a light inlet 18 and measuring the quantity of transmission of transmitted light extracted from a light outlet 19, so that test/analysis is conducted. Alternatively, the introduction of obtained mixed substance 17 into secondary mixing portion 8 and the introduction into photodetection channel 9 can also be performed by rotating the microchip around first rotating axis 12 and thereafter rotating the microchip around second rotating axis 15.
According to the microchip described in the pamphlet of International Patent Laying-Open No. 05/033666, as hereinabove described, treatments such as extraction of the target component in the sample, measurement of the target component and mixing with the reagent can be performed by rotating the microchip with the two rotating axes, i.e., first rotating axis 12 and second rotating axis 15 to apply centrifugal force of a proper direction.